Cycle 22 Abstract Catalog (Based on Phase I Submissions) Proposal Category: GO Scientific Category: Solar System ID: 13633 Program Title: A Kuiper Belt Object for the New Horizons Mission Principal Investigator: John Spencer PI Institution: Southwest Research Institute The Kuiper Belt is arguably the most important discovery in planetary science in decades. On behalf of the New Horizons (NH) mission, we propose to use WFC3 to identify KBO flyby targets for NH. This proposal will also significantly improve knowledge on two crucial scientific questions: the size-frequency distribution and the binary fraction of 30-50 km diameter KBOs, providing important constraints on disk accretion and fragmentation processes of interest to both solar system and extrasolar planet origins. STScI's Director has committed both 40 DD orbits and early implementation in summer 2014 to this GO effort. The 2002 Planetary Decadal Survey ranked Pluto-KBO exploration at the top of the NASA medium-scale mission queue and cited the KBO flyby as a fundamental mission objective. There is no prospect of a KBO flyby by any other mission than NH. Intensive ground-based searches for a flyby target since 2011 have been unsuccessful, and offer a <50% chance of success in 2014, likely leaving the KBO mission with no accessible targets. But owing to its small and stable PSF, and zero chance of weather loss of observing time, we estimate an ~94% chance of finding a targetable KBO with this proposed 2014 HST program. Hubble is the only high- probability means to rescue the exploration of the Kuiper Belt; no other NASA orbital asset can. A discovery in 2014 is required to achieve the needed one-year tracking arc for an 2015 spacecraft targeting maneuver; as described below, discovery delay to 2015 reduces the probability of detecting a KBO within the fuel budget of NH to <15% by groundbased techniques and <55% by HST Proposal Category: GO Scientific Category: Unresolved Stellar Populations and Galaxy ID: 13639 Program Title: Resolving Lyman-alpha Emission On Physical Scales < 270 pc at z > 4 Principal Investigator: Matthew Bayliss PI Institution: Harvard University We propose ACS-WFC Ramp narrowband imaging of six strongly lensed Lyman-alpha Emitters (LAEs) at z > 4 that will spatially resolve the Lyman-alpha line emitting regions on scales < 270 pc. The best available observations (HST, Spitzer, 10m ground based telescopes) are unable to provide robust measurements of the structure of these galaxies from blank field studies, but strong gravitational lensing provides a unique opportunity to peer into the heart of young star forming galaxies at high redshift and address outstanding questions regarding their morphology and evolution. Strong lensing magnifies each of our target LAEs, increasing the effective spatial resolution of ACS-WFC such that the point spread function will correspond to physical scales < 270 parsecs within all six z > 4 galaxies. Additionally, the boost in flux due to gravitational lensing makes our proposed targets the brightest sources of their kind at these redshifts, in spite of the fact that they are intrinsically ~L* LAEs. The proposed observations will probe the 1 7/1/2014 Cycle 22 Abstract Catalog (Based on Phase I Submissions) signal-to-noise and spatial resolution comparable to studies of Lyman-alpha emitting galaxies in the z ~ 0.1 universe. The resulting data will bridge the gap between deep ground-based studies of blank field LAEs at high redshift, and detailed studies of low-redshift LAEs. Proposal Category: GO Scientific Category: Cool Stars ID: 13640 Program Title: A direct probe of cloud holes at the L/T transition Principal Investigator: Esther Buenzli PI Institution: Max-Planck-Institut fur Astronomie, Heidelberg Understanding cloud formation, evolution and dispersal is one of the biggest challenges in the field of substellar atmospheres. At the transition from L to T type brown dwarfs, thick silicate and iron clouds disappear below the visible photosphere and the spectra are altered dramatically despite little change in effective temperature. Observed strengthening of the FeH band through the transition has indicated an opening of cloud holes rather than gradual sinking of the clouds. This view has been supported by the discovery of brown dwarfs with photometric variability attributed to patchy cloud cover. However, our recent spectral variability observations have complicated the picture because patchy cloud models with cloud holes currently cannot reproduce the color variations and spectral variability signatures. Whether this implies an absence of cloud holes (in contradiction to the interpretation of the observed strengthening of FeH) or is because models neglect other mechanisms that can affect the colors (eg temperature anomalies) remains unclear. Here, we propose WFC3/G102 spectral variability observations of the very nearby L/T transition benchmark binary Luhman 16AB, the only known variable brown dwarfs in a binary system. These observations target the FeH band. As the FeH molecule contains the cloud forming atom Fe, it is a direct tracer of the cloud holes. By comparing the variability amplitude in the FeH band with the surrounding continuum, as well as between the L and T component at different stages of cloud evolution, we will obtain direct evidence whether the formation of cloud holes is indeed the driving mechanism behind cloud dispersal at the L/T transition. Proposal Category: GO Scientific Category: Unresolved Stellar Populations and Galaxy ID: 13641 Program Title: A Detailed Dynamical And Morphological Study Of 5<z<6 Star, Dust, and Galaxy Formation With ALMA And HST Principal Investigator: Peter Capak PI Institution: 2 7/1/2014 Cycle 22 Abstract Catalog (Based on Phase I Submissions) We propose WFC3-IR imaging for a unique sample of 10 ~L* "normal" 5<z<6 galaxies for which direct dust dust continuum emission and dynamical measurements from the CII 158um line obtained with ALMA. This is the first, and currently only sample of z~5-6 "normal" galaxies with direct and robust measurements of their dust content, star formation rates, and dynamics. These objects will provide a representative sample of galaxies in the primordial universe that will be used for a wide range of studies. Furthermore, the dense spectroscopic sampling at z>5 from Keck and VLT along with the wealth of multi-wavelength data in the proposed COSMOS field ensure the physical properties and local environment of these sources is known. Immediate studies with the proposed WFC3-IR data include: 1) Measuring the rest-frame Ultraviolet (UV) spectral slopes to calibrate the infrared-excess - UV-slope (IRX-beta) relation which is an essential ingredient in estimating star formation rates at z>5 (e.g. Bouwens et al. 2012, Finkelstein et al. 2012), but is currently determined at z~0-2 and expected to strongly evolve at higher redshift (Meurer et al. 1999, Reddy et al. 2010,2012). 2) Compare quantitative morphologies with the ALMA dynamical measurements, constraining the formation mechanisms of these galaxies. 3) Significantly improve the spectra-energy distribution fits used to estimate stellar masses, which when combined with the dynamical mass estimates and atomic line data will test for biases in the mass estimates. Proposal Category: GO Scientific Category: Hot Stars ID: 13642 Program Title: The evolutionary link between low-mass X-ray binaries and millisecond radio pulsars Principal Investigator: Nathalie Degenaar PI Institution: University of Michigan Low-mass X-ray binaries (LMXBs) and millisecond radio pulsars (MSRPs) are two different manifestations of neutron stars in binary systems. They are thought to be evolutionary linked, but many questions about their connection remain. Recent discoveries have opened up a new vista to investigate the LMXB/MSRP link. The neutron star XSS J12270-4859 was recently observed to switch between the two different manifestations. Here, we propose to exploit the unique UV capabilities of the HST to search for the presence of a quiescent accretion disk and to test if the neutron star is hot. This will give insight into its accretion history and the mechanism driving its metamorphosis, which will have direct implications for our understanding of the LMXB/MSRP evolutionary link. 3 7/1/2014 Cycle 22 Abstract Catalog (Based on Phase I Submissions) Proposal Category: GO Scientific Category: ISM and Circumstellar Matter ID: 13643 Program Title: Imaging the tenuous dusty atmosphere of edge-on protoplanetary disks Principal Investigator: Gaspard Duchene PI Institution: University of California - Berkeley In a successful Cycle 19 survey for edge-on protoplanetary disks, we have discovered that some, but not all, protoplanetary disks present a tenuous atmosphere detected in scattered light, thus containing dust grains, located well above the optically thick disk surface. This atmosphere could be direct evidence for the super-heated region above the disk surface due to direct illumination from the central star or for a disk wind that carries along the smallest dust grains from the disk surface. Here we propose to obtain the first F475W images of a sample of six edge-on protoplanetary disks, four of which were discovered in our Cycle 19 survey, in order to constrain the characteristic grain size in the disk atmosphere and establish whether the presence of this atmosphere correlates with other disk properties. With our carefully selected sample, we will correlate the properties of the disk atmosphere with other properties of the system, such as presence of a collimated jet, dust settling and grain growth, thus providing a first empirical analysis of the nature of this phenomenon. Proposal Category: GO Scientific Category: Cosmology ID: 13644 Program Title: CIII] Emission in z=5.7 Galaxies: A Pathfinder for Galaxy Spectroscopy in the Reionization Era Principal Investigator: Xiaohui Fan PI Institution: University of Arizona The last few years has witnessed a rapid increase in the detections of galaxies at z>7, at the end of the reionization era.